Marketing requirements for pistachio nuts in the United States typically require that substantially all of the nuts have open sutures. Usually, 80 to 85% of a normal crop of pistachio nuts will have open sutures when they are picked from the tree. However, the remaining nuts generally referred to as "closed shell" nuts, are either only partially open or completely closed, in either case making them difficult to open by the consumer.
As used herein, the term "suture" refers to the longitudinal seam of the nut. When the suture is open, the seam is separated into two halves around one end of the pistachio nut and a majority of the length longitudinally of the nut.
There has existed a need for efficient and reliable techniques to split unopened or partially opened pistachio nuts in a uniform manner so that they resemble naturally opened nuts. It is important, that pistachio opening equipment be capable of operating at high speeds and that such equipment does not crack the shells of the unopened pistachio nuts other than along the sutures.
According to this invention, there is provided a continuous process of treating and splitting closed shell pistachio nuts, and a specific splitting apparatus to be used either alone or in conjunction with the other techniques and apparatus of the invention. Both the apparatus and the process developed are capable of continuous use for the rapid treatment and splitting of pistachio nuts.